Ear protector



NOV. 3, 1959 STEWART 2,910,980

EAR PROTECTOR Filed May 20, 1957 I v f BYRM W}L- United t s P e o This invention relates to a new method of ear protection employing asilicone r bber filler for the pinna of the ear.

Various attempts have been made to provide acoustic guards for the ears to protect the sensory cells of the inner ear from high and low frequency sound waves common to irritating noises such as those in present day manufacturing plants. Whereas some of these guards 'have been plainly ineffective and some have been effective and expensive, more often the primary fault of these guards has been their tendency to cause discomfort to the wearer. Although the wearing-of uncomfortable ear procolors can be enforced in; military organizations to protect the wearer from debilitating noises, this is not true in civilian life. Consequently, where prescribed ear protectors, have been discarded due to discomfort to the employee-wearer resulting in ear damage, the employer has been held liable for such injuries.

It should be borne in mind that the tympanic membrane constitutes a complete physical partition between the auditory meatus and the cavity containing the tympanum, which cavity is connected to the mouth cavity by the Eustachian tube. This tube, in its pneumatic functioning, is intended to eilect abalance in air pres- :sure between the auditory meatus and the tympanic cavity. This function is effective when air pressures vary gradually, but it fails completely with the violent pressure change in the auditory meatus caused by sudden intense sound waves. It has been the purpose of all car protecting devices to annul the injurious eflfect of this air concussion.

There have developed two gefier'altypes of ear protect'o'rs', the ear plug and the ear shell. The ear plug is designed to enter't'h'e' auditory meatus itself, an extremely dangerous proceeding, and seal i't off to" prevent the air concussions of noise sound waves hitting the tympanic membrane. However, the auditory meatus is very tender beyond the entrance, and the hair follicles endeavor to force out anything therein; if the foreign substance resists, then irritation of the canal is automatically induced. This irritation is increased where dirt and wax are transmitted into the canal by the plug. The plug is held in place by the pressure of the plug on the canal wall which must be uncomfortably distended by the plug in order to give an effective seal. In spite of the tight fitting of such ear plugs, as the wearer moves about, talks or chews gum, the plugs become loose and therefore ineffective. Consequently, when the plugs are tight, they hurt the car; when the plugs are loose, noise hurts the ear.

The ear shell on the other hand is designed to cover at least the ear and sometimes the bony structure behind the ear with materials which damp noise sound waves. This damping is usually effected at material interfaces in the sound filtering media. While these ear shells are usually very elficient, they are also costly. Ear shells are generally held in place by some sort of spring or elastic headbinding which becomes very uncomfortable 2 after aperiod of time due to the constant pressure on the skull. If the support is too loose, the ear shells fall off. The external support also has a tendency to get caught up, in the hair andin any objects which come close to the head. Furthermore, car shells are sumciehtly bulky [as to be inconvenient for wear with any confining headpiece. A I

All the previous ear protectors have suffered fro'm 'at least one of the following defects. Some have been worn in the auditory canal causing uiidue pressure andirritation. Some have been bulky; Some have been affected adversely by ear secretions. Somehave required auxiliary support. Some have proved to be toxic and irritating to the skin after'lorig wear. Some have been poorly fitted. Some have been expensive. Some have been poor in body heat transmission, thereby causing the ear to perspire. Applicants invention has none of these faults.

Applicants ear protector is made of silicone rubber, is light, odorless, self-supporting, non-toxic, small, customfitted, relatively inexpensive, resistant to ear secretions, a good transmitter of heat and applies no pressure to the auditory canal. Furthermore, applicants ear protector effectively reduces the sensitivity of the ear to the percussion of intense sound waves. I

This invention relates toj a method of protecting the tympanic membrane and of the ear which comprises filling the pinna and the mouth of the auditory canal with an unvulc'aniz'ed organopolysiloxane rubber which vulcan'ig es at room temperature and allowing the rubber to cure,- wher'eby the ear protector so formed substantially reduces the concentration of sound waves into the external auditory canal. This invention is unique in (1) employing ar oo'rn temperature-vulcanizing organepolysiloxane rubber to 2) form a custom-fitting ear protector which applies a of pressure to the wall of the auditory canal and which is completely supported by the ear. g I

The principle of this invention is entirely difierent from that of the ear plug or car shell in that by mechanical means the pinna of the ear is prevented from focusing and concentrating sound waves into the external auditory canal toward the tympanidm ernbrane. Interfering in this way with the focusing of sound waves substantially reduces the number of extraneousnoise waves which reach the tympanic membrane and ear drum. To accomplish this the auditory canalis blocked withcotton" and the pinna issubsequently filled with an organosilox'arle rubber which cures at' room temperature. The resulting molded article is custom-fitted to the ear, lightweight,

comfortable and effective.

The accompanying drawings illustrate one embodiment of this invention. Figure 1 shows the ear. Figure 2 shows a typical embodiment of this invention, Figure 3 shows the ear 'with the ear protector inserted.

More specifically Figure 1 shows the parts of the pinna of the ear: the helix 11, antihelix 12, fossa of the antihelix 13, antitragus 14, tragus 15, lobe 16 and concha 17; the auditory canal 18 and the tympanic membrane 19. q

In the preferred practice of this invention the auditory canal 18 is essentially filled with cotton. Fluid unvulcanized silicone rubber which will vulcanize at room temperature is applied to the pinna of the ear so that it fills the mouth of the auditory canal as well as the fossa and the concha but does not overlap the helix. The rubber is then allowed to vulcanize, and the resulting article is removed from the car. When the vulcanized ear protector is removed, the cotton in the auditory canal is drawn out with it and is severed from the rubber product after which the ear protector looks similar to that of Figure 2. This figure shows the finished product. The

f atented Nov. 3, 1959 part which fits into the mouth of the auditory canal is the protuberance on the right side of the figure.

An ear fitted with an ear'protector of this invention is shown in Figure 3 with the helix 11 and lobe 16 exposed and the pinna otherwise filledwith silicone rubber. The embodimentof this invention can extend over or beyond the helix or lobe if desired without departing from the scope of this invention. If it is reduced in size to cover less area than called for inthe claim, there will be a corresponding decrease in sound attenuation. In Figure 3, the drawing is out of scale in that the ear protector need not extend any appreciable distance into the auditory canal but may do so, as shown in the drawing.

The silicone rubber employed in this invention has two limitations. First, it cannot contain irritants in sufficient proportion to injure the ear. Second, it must be a formulation which vulcanizes essentially at room temperature or at most a temperature which is sufficiently low to be comfortable to the person being fitted. Otherwise any silicone rubber which vulcanizes at or near room temperature is operative herein. Specific examples of such silicone rubber formulations are shown in the copending applications of Keith E. Polmanteer, Serial No. 632,630, filed January 7, 1957 and Robert R. Selfridge, Serial No. 554,636, filed December 22, 1955, the disclosures of which are hereby incorporated by reference in this application.

turned his head to the right and then to the left, opening and closing his mouth 25 times in each position to The rubber formulations can be modified as shown in the above cited copending Polmanteer application. Furthermore, the actual composition of the ear protector can be modified, for instance, by imbedding silicone or organic foams or other sound-deadening materials in the rubber as it cures or by making a laminated article, i.e. adding layers of different materials. However, it is preferred that the surface of the protector be continuous to facilitate handling and cleaning.

Fourteen persons were fitted with ear protectors of this invention. The silicone rubber composition employed consisted of 100 parts by weight of a dimethylpolysiloxane fluid (8,000 cs.) having some silicon-bonded hydroxyl groups, 50 parts by weight of a diatomaceous earth, 4 parts by weight of a fluid methylhydrogenpolysiloxane and 3.5 parts by weight of dibutyltin dilaurate.

In each case a cotton plug was inserted in the auditory canal of the ear. While the ear was held in a horizontal position, the fluid silicone rubber composition was applied with a spatula so as to fill the outer ear. The rubber was allowed to vulcanize, and the resulting article was removed. The cotton plug was removed.

This invention was compared to the best commercial rubber ear plug. In each case the article tested was inserted properly into the ear after which each subject duplicate normal stresses applied to the plugs. Subsequently, the threshold of hearing was determined in a free-field determination with a variable external sound source placed on foot from the subject. The threshold of hearing was found for each of a series of frequencies.

Finally, the threshold of hearing was similarly determined with no ear protection. The attenuation in decibels of the various frequency sound waves by each ear device for each subject was calculated and averages taken to give the following table:

Average Attenuation (decibels) Sound frequency (cycles per second) Silicone rub- Commercial her ear ear plug protector Ear protectors of this invention have been in continuous use for two months in one department of a commercial chemical plant, whereas the commercial ear plugs were used for an average of 3 days before being discarded as excessively uncomfortable.

That which is claimed is:

An article of manufacture which comprises an organopolysiloxane rubber ear protector, one surface of which is designed to conform precisely to the surface of the outer ear, which protector covers an area at least coextensive with the antihelix, the fossa of the antihelix, the tragus, the antitragus and the concha of the pinna and the mouth of the auditory canal.

References Cited in the file of this patent UNITED STATES PATENTS 1,755,775 Dunn Apr. 22, 1930 FOREIGN PATENTS I 8,960 Great Britain Feb. 12, 1914 OTHER REFERENCES Silicons and Their Uses, (McGregor), published by McGraw-Hill (New York), 1954, pages 188 and 206 relied on. (Copy in Div. 50.) 

